This invention relates to a jig for mounting a front derailleur having a pair of guiding plates, on a frame of a bicycle in a proper position to correspond with the front chain gears.
The front derailleur should be mounted on the bicycle frame by keeping its guide plates in a position corresponding with the front chain gear.
For this purpose, a tightening band, which fixes the front derailleur to the bicycle frame, is adjusted in position by being moved vertical to or rotated around the frame. The adjustment is carried out visually with difficulty and considerable time and at present depends on only the sight of a worker. Hence, the front derailleur is often inaccurately set which results in a lowering of speed-change efficiency or the production of noise. Furthermore, a drive chain can escape from the front chain gear when changing the bicycle speed.
In the light of the aforesaid problem, this invention has been designed. An object of the invention is to provide a jig through which the front derailleur is readily mountable on the bicycle frame so as to be properly positioned with respect to the front chain gear.
The jig of the invention comprises a main body disposed opposite to a lateral side of one guide plate at the front derailleur and having a length extending along the lateral side. The main body has a receiving plate having a receiving face of circular arc to be fit to the lower end face of the guide plate and an engaging portion positioned at the lower portion of the receiving plate and engageable with the outer peripheral portion of the front chain gear. The receiving face, when the engaging portion engages with the outer peripheral portion of the front chain gear, is adapted to be set in the proper position with respect to the chain gear, so that the guide plate is located along the receiving face to set the front derailleur in its proper position.
Accordingly, the front derailleur is mountable readily on the bicycle frame in a simple operation using the jig of the invention so that the guide plate of the derailleur may be set in the proper position with respect to the front chain gear.
These and other objects and novel features of the invention will be apparent from the following description of an embodiment of the invention in accordance with the accompanying drawings.